Researchers had 40 volunteers—sometimes with dry hands, other times with wrinkly, wet ones—grab 52 items (including small and large glass marbles, rubber balls, and brass weights), one item at a time, with their thumb and forefinger and then pass each object through a 5-by-5-centimeter hole. In some tests, the hole was 45 cm above the table top; in the others it was 75 cm. On average, volunteers with wrinkly fingers completed the task no more quickly than their dry-handed counterparts...

The previous study used fewer objects, like glass marbles and lead fishing weights, and used half as many participants.

A second experiment showed that water-wrinkled fingers were no more or less sensitive than smooth ones. Consequently, the researchers say pruny fingers don't confer any kind of evolutionary advantage.

Instead, the researchers suggest that finger wrinkles are just a byproduct of immersing them in warm water. It's an automatic response triggered by our nervous system, one that happens to cause vasoconstriction — the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels.